Dell XPS 13 with a 2560x1080 Ultrawide Monitor

The other questions that are asked are poorly worded and never really arrive at a solution.

I just purchased an LG ultrawide monitor with 2560x1080 resolution and also a Dell XPS 13. I cannot seem to get these to work together. I have the Dell USB C -> HDMI connector. I also have a third party 4k USB C to HDMI connector. Both of these only push out a resolution of 1920x1080. I get a message on my external monitor saying:

"The screen is not currently set to the recommended resolution...

This is worrying. Is there any adapter / dock in the world I can buy to get this resolution? This is very important to me. Otherwise I would have to return the XPS.

Please provide links to docks/cables that have worked for you. I read somewhere that a USB-c to Display port adapter has worked for some people. There is one on the dell website. Will this work?

Need asap.